In the prior art technique, microscopic switches of the size of several hundred micrometers have been known, as described in IEEE Microwave and Wireless Components letters, Vol. 11 No. 8, August 2001, p 334.
FIG. 1 is a cross sectional view showing the configuration of a conventional switch 10 as described in the above reference, and FIG. 2 is a top view of the conventional switch 10. FIG. 1 is a cross sectional view along A—A line of FIG. 2. This switch 10 has a membrane (Switch Membrane) on which a signal line 11 for transmitting high frequency signals is formed, while a control electrode 12 is provided directly below the above signal line 11.
When a DC potential is applied to the control electrode 12, the membrane is attracted to the control electrode 12 by electrostatic attractive force, and bends so as to come into contact with a ground electrode (Ground Metal) 14 formed on the substrate 13, so that the signal line 11 formed on the membrane is short circuited, to attenuate and block the signal passing through the signal line 11.
In contrast to this, when no DC potential is applied to the control electrode 12, the membrane does not bend, so that the signal passing through the signal line 11 formed on the membrane can pass through the switch 10 without loss from the ground electrode 14.
However, in the case of the conventional switch 10, the DC potential required for attracting the membrane to the control electrode 12 is 30 V or higher, and there is a problem that it is difficult to implement a mobile wireless terminal with the switch 10 requiring this high voltage.
Also, when the membrane is attracted to the control electrode 12 to block the signal, the impedance of the signal line 11 is short circuited, and reflection occurs when the high frequency signal passes, to make it necessary to provide parts such as a circulator and the like.